As the Supreme Court gets ready to consider the validity of EPA’s Cross-State Air Pollution Rule, some of the Northeastern and Mid-Atlantic states are taking another tack to address at least part of the air pollution transport issue. They have petitioned EPA under § 176A of the Clean Air Act to add Illinois, Indiana, Kentucky, Michigan, North Carolina, Ohio, Tennessee, Virginia, and West Virginia to the Ozone Transport Region established under § 184 of the CAA.

As the Technical Support Document submitted with the Petition indicates, the OTR states (minus their members with Republican governors) have largely relied on the same modeling that EPA used in developing CSAPR. Shrewd, if obvious, move.

It’s not clear whether the OTR states would have filed this Petition if CSAPR had been upheld by the Court of Appeals or, relatedly, what would happen to the Petition were the Supreme Court to decide in EPA’s favor in the CSAPR case. This may be just a backstop.

It’s certainly a substantial backstop. I don’t think that the underlying science is seriously in question, even if the proposed new states might be able to challenge it on the margin. If it gets that far, I’d assume that the Petition will be granted.